The present invention relates to a magnetic transducer with a built-in step-up transformer and, more particularly, to a magnetic transducer having a single turn signal winding coupled to a step-up transformer which is integrally assembled with a magnetic ring head core. Still more particularly, the invention is concerned with a construction of a step-up transformer in which the transformer shares part of its magnetic path with a rear portion of a magnetic ring head core.
The art of magnetic recording now encompasses a wide range of applications including those used in video, digital, instrumentation and audio recording. Most of these recording systems employ a so-called ring head, a magnetic transducer defining a substantially closed magnetic circuit including a pair of core halves separated by a front non-magnetic gap and defining an internal coil winding aperture, with multi turns of winding being disposed about the core half through the coil winding aperture to be interlinked with the magnetic circuit of the transducer. Transducers used in these systems of course take a great many forms, and various disclosures have been made so far concerning their construction designs, preparation techniques and so on.
In the prior art of ring head construction, however, complications are usually encountered with the winding processes of multi-turn signal coils. This is particularly true of those high frequency recording and reproducing transducers typified by video heads in which the winding aperture is usually extremely small to assure high flux transfer efficiency of the head core: in most cases the winding aperture is too small to be machine-managed, the unavoidable results often being the necessity for exhausting manual labor coil winding processes.
This is where a single-turn transducers can be effectively introduced with step-up transformers being integrally incorporated in the transducers to be coupled with the single-turn winding. This is schematically shown in FIG. 1, where 1, 2, 3 and 4 designate a ring head core, a single-turn signal winding, a step-up transformer and junction lead portions, respectively.
The type of transducers as shown in FIG. 1 will hereinafter be referred to as single-turn step-up transducers, while transducers having multi-turns of windings about their ring head cores and no built-in transformers will be referred to as multi-turn direct-winding transducers.
It should be noted here that the object of single-turn step-up transducers is not the provision of transducers superior in recording and reproducing performance to multi-turn direct-winding transducers: single-turn step-up transducers only reach comparable levels of performance with their multi-turn direct-winding counterparts when transformers are 100% loss free and single-turn windings are of zero electrical resistance. The object rather is to provide one possible form of transducer which greatly reduces complications in the winding processes associated with multi-turn direct-winding transducers, while of course maintaining comparable transducer performance.
Upon designing a single-turn step-up transducer, therefore, the transfer efficiency of the transformer portion is of vital importance to any type of application, and special considerations have to be given to particular requirements. Reduction of electrical resistance of the single-turn winding is also another important design consideration, since it is directly connected with lowering of the transducer impedance and improvement of transfer efficiency, which are particularly benificial to high frequency applications. Yet another and probably the most important matter, above all, is the construction design by which the winding processes can be completely machine-managed or automated, since such a transducer is one possible answer to the question: how can one put an end to those manual labors?
FIGS. 2 to 4 show some of the conventional embodiments of single-turn step-up transducers.
Referring first to the construction in FIG. 2, 12a and 12b are head core halves constituted by a pair of plate-like magnetic materials. The head core half 12b has a single-turn winding 11 and a multi-turn transformer winding 10 is provided on the other head core half 12a to form a magnetic coupling, and the single-turn winding 11 forms an electrically closed circuit through a signal winding aperture 13a and a transformer winding aperture 13b. Thus integrally constructed by using core halves 12a, 12b partly in common are a ring head portion 5 and a transformer portion 6 having a non-magnetic operating gap 9 and the main flow of magnetic flux along the path 7 and the path 8, respectively.
The defect in the construction in FIG. 2 is that the single-turn winding 11 and the transformer winding 10 must be positioned only after the core halves 12a and 12b are joined together, thus making the automatic disposition of the windings, transformer winding 10 in particular, quite unpractical. This is because the joining of the core halves is usually done by means of glass, brazing or the like to assure a firmly defined non-magnetic gap and sufficient bonding strength, and the high-temperature bonding treatment inevitably precedes the disposition of either winding 10 or 11.
FIG. 3 shows a construction basically similar to that shown in FIG. 2, but the core half 12b in FIG. 2 is divided in two: the core half 12c and c-shaped transformer core 12d in FIG. 3, thus forming the ring head portion 5 and the transformer portion 6 integrated together. In this construction the core halves 12a and 12c may first be joined by glass, brazing or the like, and then the c-shaped transformer core 12d with the transformer winding 10 being disposed on it can be joined to the rear portion of the head core half 12a by means of a low-temperature adhesive material 14 such as an epoxy resin. The single-turn winding 11 is subsequently positioned to encompass the head core half 12c and the transformer core 12d through the apertures 13a and 13b. Thus automated winding processes may be carried out relatively easily.
In the construction of FIG. 3, however, the adhesion area between the core half 12a and the transformer core 12d is largely restricted by the thickness of the core half and the transformer core, which, for example, is usually less than 200 .mu.m for a typical video head configuration. This may cause a serious lack of bonding strength when the bonding material is a resin or the like which is almost inevitable for this construction.
Referring now to FIG. 4, a pair of core halves 15a, 15b is joined to form a ring head core with an internal coil winding aperture which is to be filled with an electric conductor 16. On either side of the ring head core are deposited thin conductor layers 17 which are in electrical contact through the conductor 16 to form a single-turn signal winding (not closed). On the other hand a step-up transformer 18 is provided with a single-turn primary winding 19 (not closed) and a multi-turn secondary winding 20. The transformer 18 is then joined to the rear edge of the ring head core, and by making an electrical connection between the conductor layer 17 and the primary winding 19 a single-turn step-up transducer is constructed, in which a ring head core, virtually, is magnetically separated from the transformer core.
The transducer having the above construction, however, possesses the shortcomings that since no cores are used in common for a ring head core and a transformer core, the transducer as a whole tends to be somewhat large in size, as well as that the transformer construction itself is not suited for an automated winding processes.
In addition to the problems of the prior art described above, a comment has to be made on the type of transformers employed. Namely transformers are usually of two types: one having a substantially ring shaped magnetic core, with non-coaxial primary and secondary windings being disposed on it as shown in FIG. 5, and the other having coaxially placed primary and secondary windings and a magnetic circuit being being positioned to couple the both windings as shown in FIG. 6. The former is called a core type and the latter a shell type, and it is generally known that the shell type provides higher transfer efficiency. As is evident from FIGS. 2 to 4, step-up transformers employed in the prior art described above are all core-type transformers and hence transducers employing these transformers tend to suffer from poor efficiency.
As is understood from the above descriptions single-turn step-up transducers according to the prior art involve problems of:
(1) difficulties in automating the coil winding processes;
(2) lack of bonding strength in the transformer portions;
(3) insufficient transfer efficiency of the transformer portions; and
(4) difficulties in assembling the transducers compactly.
There is one more shortcoming of the conventional embodiments, although it might be too much to describe it as a shortcoming of the transformer itself, which is that since transformer windings protrude to either side of the transducers of the conventional embodiments, it is difficult to laminate the transducers to form multi-channel transducers.